Did anyone ask George Lucas how long filming “Star Wars” would take?
Did the Pope ever ask Michaelangelo how long the Sistine Chapel would take?
Okay, maybe those are bad comparisons. More accurately, it would be like asking a personal trainer how long it would take to get someone in shape. Are we talking about losing 25 lbs. to look good for your class reunion or long-term health that will improve your body, energy, and quality of life.
So I would ask you: What shape is your website in? Is it sitting around doing nothing or at least taking walks?
What’s your overall objective with your web page? Do you need a sprint for a short burst of attention or are you going the distance and working to increase traffic months from now?
What action do you want to come from your visits? How often do you want people to come visit and what do you want them to do once there?
To get back to the apologetically vague answer: it depends on the size of your site, your goals, and how proactive you want to be. I’ve worked with people for just a few hours and I have other projects that still need on-going, monthly support.
I like to view web analytics in terms of long term health–maybe you need some extra attention up front and then move to a few hours for monthly check-ups.